1. Field of the Invention
The invention concerns a system and a method for data transfer between a rotatable part and a stationary part of a gantry of a computed tomography apparatus. The invention also concerns a computed tomography apparatus having such a device for data transfer.
2. Description of the Prior Art
A computed tomography apparatus, in particular an x-ray computed tomography apparatus, has a gantry with a part that can rotate relative to a stationary part. On or in the rotatable part are arranged (among other things) an x-ray source and an x-ray detector opposite one another. In the operation of the x-ray computed tomography apparatus, large quantities of measurement data accumulate during the acquisition of x-ray projections. The measurement data must be transferred from the rotating part to the stationary part of the gantry since the processing of the measurement data—in particular the reconstruction of slice images and 3D images based on the measurement data—normally ensues with an image computer located on the stationary side.
Furthermore, in the operation of the x-ray computed tomography apparatus bidirectional operating data of the x-ray computed tomography apparatus (including control data, status data etc.) must be transferred from the stationary part to the rotatable part of the gantry and from the rotatable part to the stationary part.
The data transfer between the stationary part and the rotatable part of the gantry can take place by mechanical contact (using slip rings) or without contact (for example by capacitive coupling. For example, in DE 10 2005 056 049 A1 a contact-less data transfer by capacitive coupling in a computed tomography apparatus is described. At least one stripline (strip conductor) pair for symmetrical signal transfer is attached on the rotatable part of the gantry; into which stripline pair the data to be transferred or electrical signals carrying the information are fed by a transmission module. At least one receiver element is mounted on the stationary part, this receiver element being located at a slight distance along at least one segment of the stripline pair during the relative movement of the two parts and is connected with a receiver module.
A computed tomography apparatus normally has multiple such data transmission links (routes) each formed by a stripline pair. A first data transmission link is present for the transfer of the measurement data acquired with the x-ray detector from the rotatable part of the gantry to the stationary part. A second data transmission link is provided for the transfer of operating data of the computed tomography apparatus from the stationary part to the rotatable part of the gantry, and a third data transmission link is provided for the transfer of operating data of the computed tomography apparatus form the rotatable part of the gantry to the stationary part. The second and third data transmission links serve to generate the redundancy that is necessary for the transfer of operating data in order to realize a secure data transmission between the rotatable part and stationary part of the gantry.
The provision and the parallel operation of the transmission links for data involves a not inconsiderable technical and financial cost.
Furthermore, an arrangement for transmission of electrical signals and/or energy between parts that are rotating relative to one another is known from U.S. Pat. No. 6,798,309 B2. A transmission unit has two annular electrical conductors, one transmitter and a termination element. The transmitter and the termination element are arranged diametrically opposite one another in relation to the annular electrical conductor. The two annular conductors are terminated, essentially without reflection (reflection-free termination), by the termination element. A high-resistance (high-ohmic) receiver has two conductors matched to the electrical conductors of the transmitter and that are not terminated with a reflection-free termination, and are galvanically, inductively and/or capacitively coupled with the conductors of the transmitter. The conductors of the transmitter are a symmetrically arranged conductor pair into which the transmitter symmetrically feed signals to be transmitted. The receiver can tap the signal by means of a slip contact, or inductively or capacitively.
The design of a PET scanner for small organisms is described by Lewellen, T. K. et al. in “System Integration of the MiCES small animal PET Scanner”, 2004 IEEE Nuclear Science Symposium Conference Record, 16-22 Oct. 2004, Vol. 5, pp. 3316-3320. The gantry of the PET scanner has a slip ring arrangement to transfer energy and analog signals.